1. Field of the Invention
The invention generally relates to a light-emitting structure, and more particularly, to a semiconductor light-emitting structure.
2. Description of Related Art
Along with the progress of photoelectric technology, the fabrication and the application of a light-emitting diode (LED) has gradually reached their ripe stage. Since
LEDs have advantages of low pollution, low power consumption, short response time and long lifetime, so that LEDs have been gradually applied in various fields of light source or illumination to substitute traditional light-emitting components such as fluorescent lamp, incandescent bulb or halogen bulb. Around the world, environmental awareness is growing and growing and thus it can be expected the LEDs would become the major illumination light source in the future to substitute the current position of the fluorescent lamp.
In general speaking, the LED's electrode disposing way can be categorized into horizontal disposing way and vertical disposing way, in which the horizontal disposing way means the two positive and negative electrodes are disposed at a same side of an LED epitaxy structure, while the vertical disposing way means the two positive and negative electrodes are respectively disposed at two opposite sides of an LED epitaxy structure. In more details, in an LED structure with the horizontal disposing way of its electrodes, the positive electrode is disposed on a p-type semiconductor layer, while the negative electrode is disposed on an n-type semiconductor layer, and the two electrodes are not overlapped with each other on a direction perpendicularly to the light-emitting layer thereof. Usually, the two electrodes are made of non-transparent metal. When the distribution area of the two electrodes is small, the situation that the light emitted from the light-emitting layer is blocked by the two electrodes can be reduced and the light extraction rate can be accordingly not decreased, however, the current flowing from the p-type semiconductor layer to the n-type semiconductor layer would be excessively concentrated in a small area between the two electrodes. As a result of excessively concentrated current distribution, it leads to non-uniformity of the emitted light and to heat-dissipation difficulty and easier damage of the LED due to the excessively concentrated heat produced during the current passing, and the LED's light-emitting efficiency is reduced. On the other hand, when the distribution range between the two electrodes is increased by design, the excessively concentrated current distribution problem can be lightened, but the electrodes would block too much light, which leads to largely reducing the light extraction rate.